Among lipid-soluble vitamins, many of them are unstable to light, heat or oxidation. Thus, stabilizing a lipid-soluble vitamin in a liquid food or drink containing the lipid-soluble vitamin has been a problem.
Known methods of stabilizing lipid-soluble vitamins include a method of stabilizing vitamin K through adding a light-sensitive lipid-soluble substance [Jpn. J. Hosp. Pharm., 22, 449 (1996), Abstracts of the 110th Annual Meeting of the Pharmaceutical Society of Japan, 4, 104 (1990)], a method of stabilizing with a light shielding cover [Jpn. J. Hosp. Pharm., 28, 47 (1992)], a method of suppressing light-induced decomposition of vitamin K2 in a solution by adding glutathione [(J. Parenteral Science & Technology, 43, 204(1989)], a method of stabilizing a lipid-soluble vitamin by uniformly mixing carotenoid with the lipid-soluble vitamin (Japanese Published Unexamined Patent Application No. 26670/92), a method of stabilizing a lipid-soluble drug which is unstable to light by blending at least one substance selected from yellow and red coloring agents (Japanese Published Unexamined Patent Application No. 7583/00) and the like.
However, there have been no reports made to date regarding effects of using a pigment or an emulsion in combination with an antioxidant to stabilize a lipid-soluble vitamin, particularly, vitamin K or ubiquinone.
Known food or drink containing a lipid-soluble vitamin include a food or drink containing vitamin K (Japanese Published Unexamined Patent Application No. 127816/99), milk and a dairy product with enriched vitamin K and calcium (Japanese Published Unexamined Patent Application No. 56232/99), a nonalcoholic beverage containing ubiquinone (Japanese Translation of PCT International Application No. 504343/01), a beverage composition containing vitamin A or vitamin E (WO96/04801) and the like.